In practice, filtration can be broadly classified into six separation categories: solids-gases, solids-liquids, solids-solids, liquids-liquids, gas-liquids, and gas-gas. Filtration technologies are used to separate contaminants and value-added materials in a wide range of process applications, such as automotive and aerospace fuel and air filtration, household and industrial air filtration, food and beverage concentration and sterilization, pharmaceutical molecule isolation and purification, medical therapeutics like kidney dialysis and blood oxygenation, potable water treatment, industrial process water purification, as well as waste treatment and environmental remediation. For example, filtration is the most important and widely used method for water purification due to its ability to completely and continuously filter impurities by size exclusion, preferential adsorption, and diffusion on a large scale (Howe and G. Tchobanoglous, Water Treatment: Principles and Design, John Wiley & Sons, Inc., Hoboken, N.J., 2nd edn, 2005). Nearly all municipal and industrial water and wastewater treatment facilities, most groundwater treatment facilities, and large and small desalination facilities employ some form of filtration for the removal of problematic material, such as microorganisms, clay, sediment, oil, and other organic and inorganic solutes (Crittenden, J., et al. (2012) Water Treatment: Principles and Design, MWH, Hoboken, N.J., USA).
Generally, fluid filtration constitutes the separation and removal of target suspended and dissolved solids from water by the relative rates of passage through a separation medium. Fluid filtration systems most commonly embody the following treatment technologies: granular media filtration (e.g., sand, anthracite, garnet, nutshells, non-woven fabrics, and other non-reactive waste biomass), ion exchange media filtration, adsorptive media filtration (e.g., granular activated carbon or GAC, zeolites, polymer and organoclays), reactive media filtration (e.g., greens and oxidative filtration, bio-sand filtration, bio-GAC filtration), low pressure membrane filtration (e.g., microfiltration and ultrafiltration), and high-pressure membrane filtration (e.g., nanofiltration and reverse osmosis).
Most filtration processes are limited by the accumulation of removed material on or in the filter medium. For example, when a membrane is used to filter impurities from a water sample, the flux will gradually decrease with time as the membrane becomes clogged or “fouled” by inorganic particulates, organic matter, and/or biological microorganisms. Membrane fouling often results in severe flux or throughput decline, affecting the process efficiency and quality of the water produced. Indeed, filter clogging and its mitigation remains the major operational challenge of filtration technologies due to dramatic effects on filtrate quality, maintaining target filtration throughput, energy efficiency and filter damage.
Filter clogging is an inevitable phenomenon that occurs during filtration, but can be mitigated by routine maintenance strategies before complete replacement is needed. Specifically, flux maintenance techniques can be defined as system processes implemented to recover filtrate flux by removing reversible foulants and deposits on or within the filter and/or inhibiting their future deposition. Common maintenance strategies include variable forms of mechanical and chemical cleaning, such as filtrate backwashing and in-situ chemical cleaning (e.g., caustics, oxidants/disinfectants, acids, chelating agents, and surfactants) (Liu, C., et al. (2006) Membrane Chemical Cleaning: From Art to Science, Pall Corporation, Port Washington, N.Y. 11050, USA). However, each maintenance response can negatively affect the efficiency of the process by increasing system downtime, consuming the commoditized filtrate product, consuming costly cleaning chemicals, and damaging the filter through harsh cleaning methods. Currently, these filter maintenance techniques are implemented using pre-determined design criteria-frequency, intensity and duration—and cannot adapt in real-time to spatial and temporal variations within a given filtration process. Therefore, there is a need for adaptive process control techniques for operating filtration-based processes in order to optimize the maintenance response and minimize the effect of filter contamination on operating energy requirements and life cycle performance.
Considerable effort is associated with responding to the removal and replacement of expired filters and can result in significant system downtime and cost. The useful lifetime of a filter module, filter media, ion exchange resin, or granular activated carbon is site-specific based upon unique environmental conditions and water quality for a given treatment objective. Therefore, maximizing plant efficiency requires the need to predict the useful life of a module(s) based on information directly associated with a specific performance of the said module(s) in a given application. These and other shortcomings are addressed in the present disclosure.